The paper presents a concomitant model based multi-level fault-tolerant control (FTC) for near space vehicle (NSV) with a new type of dissimilar redundant actuation system (NT-DRAS). The model, with its physical meaning as a virtual system of the actual vehicle, coexists with the real system to perform real-time synchronous simulation and monitoring of the real system's functions and performance status. In order to meet the intelligent decision-making support requirements of the NSV actual system, the concomitant big model consists of a flight control-level main model and actuation-level sub-models that form a hierarchical architecture. In the event that the vehicle's flight attitude-related sensors fail, a hybrid output state can be reconstructed by combining the theoretical output of the flight control-level concomitant main model with the real system usable state. This hybrid output state is then used to solve the state feedback gains using linear quadratic regulator (LQR) technology. Additionally, this study conducts state monitoring and redundancy management for the configured NT-DRAS system at the actuation level, ultimately combining concomitant sub-model based NT-DRAS channel switching measures by flight control-level concomitant main model based LQR control to address complex and progressively deteriorating fault conditions involving actuators and flight control attitude sensors. Finally, numerical simulations are performed on the MATLAB/Simulink platform to verify the effectiveness and progressiveness of the proposed method.

The environmental wind tunnel of high-speed railway trains serves as a crucial experimental facility for the research and development of high-speed railway technology. The refrigeration system within the wind tunnel is an important subsystem. However, the design of the wind tunnel refrigeration system management program presents significant scientific challenges and limitations. Traditional management approaches in wind tunnel refrigeration systems suffer from prolonged decision-making times and reliance on experiential knowledge, necessitating the need for intelligent transformation. This paper aims to address these issues by exploring existing intelligent management methodologies and defining the concept of a wind tunnel intelligent laboratory along with its primary modules. Furthermore, we propose a water cooler failure prediction model based on the existing equipment model of the wind tunnel's refrigeration system. This model effectively predicts the remaining useful life (RUL) of the water cooler in the case of fouling failure, contributing to enhanced efficiency, cost reduction, and safety improvements in laboratories

Accurate and efficient prediction of propeller aerodynamic performance and tonal noise is essential for low-noise aircraft design, yet hybrid CFD/CAA simulations remain prohibitively expensive, especially when uncertainty quantification (UQ) is required. To address these limitations, this study develops a three-fidelity variable-fidelity deep neural network (VFDNN) surrogate model with an explicit fidelity indicator and integrated heteroscedastic UQ head for uncertainty-aware propeller blade shape optimization. Low-fidelity (LF) data are generated by a BEMT-based frequency domain method, whereas medium- (MF) and high-fidelity (HF) data are obtained from coarse- and medium-grid CFD simulations coupled with the FW-H acoustic analogy using a pseudo-rotation strategy. The VFDNN integrates LF/MF/HF sub-networks with a hierarchical correction module to deliver HFlevel predictions of thrust, propulsive efficiency and 1st BPF tonal acoustic pressure along with calibrated predictive intervals. Compared with an HF-only MLP and two dual-fidelity baselines (MFNN and LambdaNN), the VFDNN achieves lower RMSE and MAE, higher R2 and near-nominal 95 % interval coverage over multiple random initializations. The calibrated surrogate is then embedded into a deep reinforcement learning optimization framework with an uncertainty-aware objective that penalizes both direction-averaged tonal noise and its predictive uncertainty under thrust and efficiency constraints. The final optimized propeller improves efficiency by about 1 % while reducing the uncertainty-aware acoustic objective by roughly 16 % relative to the baseline, and URANS-based FW-H simulations confirm a 2.4-5.9 dB reduction of the first three BPF tones at the lateral observer with nearly unchanged thrust. An equivalent-iteration analysis further indicates that replacing direct CFD-driven optimization with the VFDNN surrogate reduces the overall wall-clock cost by approximately 68 %, demonstrating the practical value of the proposed framework for high-dimensional, uncertainty-aware low-noise propeller design under limited HF data.

The new type dissimilar redundant actuation system (NT-DRAS) can be used in high value near space vehicle (NSV) due to its advantages of flexible layout and high mission reliability with dissimilar redundancy. It can have different operation modes, in which the working channels from the current one to the other backup one can provide active fault tolerant control (AFTC) strategy, the switching criterion remains a problem for the NT-DRAS. This paper proposed a flight quality constraint based AFTC (FQC-AFTC) strategy for the NT-DRAS channel switching problem. The linear-quadratic (LQ) cost function is used as index form to evaluate the flight quality of the flight control model, both the NT-DRAS channel switching error threshold and fault tolerance response time are considered to derive a comprehensive LQ cost function index, and then the channel switching (AFTC) strategies are given based on the LQ cost function index under different conditions. Simulation analysis and studies are performed to verify the proposed FQC-AFTC effectiveness finally.

The abstract A 6-DOF reconfigurable parallel platform has been designed and it can rely on a frame to implement the structure changes between the four kinds of parallel platforms. One of the structures is selected to do the kinematics analysis to establish the position, velocity and acceleration model. According to the motion characteristics of parallel platform, using two kinds of trajectory planning method that the 3-4-5 times polynomial motion law and 7 times B-spline motion law in operating space simulate its movement situation. With the same trajectory, the simulation contrasts analysis the joint velocity, acceleration and torque curves under the two kinds of methods. From the curves, it can see that the parallel platform motion joint curves by the latter law are relatively steady and low jitter, and the acceleration curves don't have the sharp point to effectively reduce the vibration and impact in the parallel platform motion. Besides, with the optimization model, the motion consumptions of the parallel platform joint and end-effector are all decreased. Finally, the parallel platform end-effector moment acceleration curve is obtained through the prototype experiment, and the results verify that the method can reduce the motion direction acceleration to make the parallel platform motion more smooth and suppress the residual vibration.

In this paper, a method for electric-resistance heating is proposed to reduce the thermal stress generated at a thick-walled pressure component during cold start-up in a coal-fired utility boiler. The aims of this approach are to shorten the start-up time and enhance the flexibility of the utility boiler. While focusing on a steam-water separator in a supercritical utility boiler, the finite element method (FEM) is employed in this study to analyze the thermal and mechanical stress amplitude and fatigue lifetime consumption parameters during cold start-up. An analysis of practical and optimized cold start-up is conducted. This start-up process involves the application of electric-resistance heating to a steam-water separator to shorten the boiler water filling time. Experiments are performed to investigate the differences in the inner and outer wall temperatures and thermal stresses under non-heating and electric-resistance heating conditions for a thick-walled component in an experimental facility being input with high-temperature and high-pressure steam. The results show that electric-resistance heating may reduce the thermal stresses and the fatigue lifetime consumption levels in thick-walled components when applied during cold start-up, and the cold start-up times are significantly shortened. The feasibility of this approach in practical engineering is confirmed through experiments.

This article investigates the issue of distributed model-free adaptive iterative learning sliding mode control (DMFAILSMC) for unknown nonlinear multi-agent systems (MASs) under denial-of-service (DoS) attacks. Firstly, considering the measurement channel is affected by DoS attacks, the compensation algorithm based on historical iteration data is devised to minimize the adverse effects. Secondly, the compact-form dynamic linearization (CFDL) technique is used to transform the compensated system into the equivalent data model along the iterative axis. Subsequently, by using one-step-ahead synchronization measurement error, the distributed sliding mode controller is developed to achieve consistent tracking of all agents. Finally, two examples have validated the effectiveness of the proposed scheme.

In order to support the fault-tolerant control (FTC) design for the new type dissimilar redundant actuation system (NT-DRAS) used in near space vehicles, this paper proposed a multidimensional fault characterization model based fault identification method. The NT-DRAS model is first introduced as well as the operating modes. The fault occurrence mechanism for the considered faults are then analyzed. Followed by the analysis results, the multidimensional fault characterization based fault reasoning mechanism is presented, and then the multidimensional fault characterization models as well as the discrimination algorithm used to identify the fault modes are presented. Simulation results are performed finally to verify both the analyzed fault occurrence mechanism and the proposed fault identification effectiveness.

With the deepening of the energy revolution, the power terminal will also usher in significant transformations, DC home appliances in building “photovoltaics-energy storage-DC-flexibility (PEDF)” system have typical features of storage-use integration, DC power supply and flexible electricity consumption. This paper focuses on the technologies and standards of DC household appliances, compares the relevant standards at home and abroad. Thus, a standard system for DC household appliances was built based on the above review, the key technologies that hinder the industrialization of DC household appliances were analyzed, and the key research contents of technical standards were proposed. Conclusively, the outlook of the future research was proposed to provide reference for further in-depth research and exploration of “PEDF” DC household appliances.

In engineering applications, the parameters of Parmanent Magnet Synchronous Machine(PMSM) are likely to be greatly deviated due to the change of environment.However, the change of electrical parameters will have a great influence on the control strategy of motor.This paper presents a parameter identification algorithm based on Levenberg-Marquardt algorithm(LM algorithm)to identify motor parameters. Firstly, the mathematical model of the motor is established. Then, the current and speed information of the motor are collected through locked-rotor and no-load experiments, and the collected information is identified by lm algorithm. The identification parameters are compared with the actual parameters to verify the effectiveness of the identification algorithm. Finally, the real current and speed information of the motor are collected by the real-time simulation simulation, so as to verify the validity and correctness of the scheme.

This paper studied the actuation system form used in near space vehicle, based on the near space vehicle design demanding of high power/weight ratio and high reliability, this paper proposes a new type dissimilar redundant actuation system (NT-DRAS). It is composed with electro-hydrostatic actuator (EHA) and electro-mechanical actuator (EMA), followed by this, aiming at high power/weight ratio and high reliability, an multi-constraint model is given first, and then multi-constraint based power/weight ratio and reliability optimization process is given. Finally, optimization results in three dimensional space are given to show and analyze that the NT-DRAS can have high power/weight ratio and high mission reliability compared with other actuation schemes.

This paper presents a concomitant observer-based multi-level fault-tolerant control (FTC) for near-space vehicles (NSVs) with a new type dissimilar redundant actuation system (NT-DRAS). When NSV flight control system faults occur in NT-DRAS and attitude-corresponding sensors, the NSV hybrid output states, including the concomitant observer usable states and the real system states, are applied to solve the FTC gain by using the linear quadratic regulator (LQR) technique. Furthermore, since NT-DRAS is used in NSVs, a multi-level (actuation system level and flight control level) FTC strategy integrating NT-DRAS channel switching and flight control LQR is proposed for complex and worsening fault cases. The most important finding is that though the proposed strategy is applicable for worsening fault cases in NSVs, systematic and accurate criteria for the process being performed are necessary and can improve the FTC efficiency with minimal FTC resources. Additionally, such criteria can improve the NSV’s responsiveness to comprehensive faults, provided that the real-time performance of the fault detection and diagnosis (FDD) scheme can be further optimized. The concomitant observer convergence and the multi-level FTC strategy have been verified by numerical simulations based on the Matlab/Simulink platform.

It is a major problem for the aircraft environmental control system (ECS) design and improvement when encountering failures during dynamic operation. The traditional ground test equipment for the ECS only can supply gas in a steady state or a small range at a low speed, and it is difficult to reproduce the environment of rapid and violent dynamic air bleed of ECS in the air. To make up for the lack of dynamic test capability of ECS, China has built a new double-engine dynamic simulation test bench for ECS with the largest parameter coverage and the highest dynamic index, which can simulate the dynamic air bleed environments of different engines under different working states for the ECS. The overall design method of the test bench was introduced in this paper. The combined adjustment of temperature and pressure was realized by the method of using the main valve for pressure regulation and mixing the cold and the hot for temperature adjustment, and the resistance relationship of each link was reasonably distributed to weaken the coupling in the pressure regulation and temperature adjustment process. The rapidity of temperature adjustment was ensured by using a bypass heater for heating and a heat exchanger for heat exchange. Double-valve linkage control was used to ensure the large range and high precision of pressure regulation, and dual flowmeters were employed to ensure steady-state measurement accuracy and dynamic measurement speed. Based on the traditional distributed control system, a fast interactive network of reflective memory cards was established to realize the fast response of the control system, and the proportional-integral-derivative (PID) algorithm based on the expert system was adopted to improve the control effect of the controller. The test results show that the test bench can rapidly and dynamically regulate pressure and adjust temperature in a wide range.

Environmental wind tunnels for high-speed trains play a significant role in their development. The cooling system of the wind tunnel poses a challenge as it requires lower temperatures and a higher cooling capacity during operation. The conventional approach to wind tunnel refrigeration uses evaporative cooling, which is less efficient at low temperatures and comes with environmental and safety risks. In this study, we propose an innovative air compression refrigeration method based on the Brayton cycle. This method converts high-pressure air into low-temperature air at atmospheric pressure for wind tunnel refrigeration. The new cooling system has reduced energy usage by 3.72 MW, leading to a 13.15% improvement. The return cooler of the system is modeled using the effective number of heat transfer units and the mean temperature difference design method. Additionally, the turbine within the system is analyzed using one-dimensional flow characteristic analysis and the principle of similarity. This method has been validated by comparing it to other published papers. Subsequently, we perform a thorough sensitivity analysis on the key design parameters of the system. We observe that with a sufficient heat transfer area of the recooler, the cooling efficiency of the system exhibits a gradual decline from 64% to 60% as the mass flow rate of the system rises. For a fixed turbine, the cooling efficiency of the system rises from 20% to 62% and subsequently declines to 37%, with an increase in the mass flow rate. As a result, we conclude that the design parameters of the turbine have a more significant influence on the cooling efficiency of the system than the recooler. Our study will establish a foundation for selecting parameters to optimize the refrigeration system in the future.

Environmental wind tunnels play a crucial role in the research and development of high-speed railways. However, constructing and operating these wind tunnels requires significant resources, especially with respect to the cooling system, which serves as a vital subsystem. The cooling system utilizes an air compression refrigeration cycle and consists of multiple components. The efficient operation of these components, along with the adoption of appropriate strategies, greatly enhances the efficiency of the wind tunnel refrigeration system. Despite this, the existing methods for evaluating the refrigeration system do not fully capture the energy consumption of an air compression refrigeration system during practical use. To address this issue and effectively evaluate the wind tunnel refrigeration system, we propose using an exergoeconomic evaluation coefficient with experimental cycles to establish the system. This method incorporates the use of frequency coefficients and related parameters. By employing the newly developed evaluation coefficient as an objective function, we utilize the adaptive value-sharing congestion genetic algorithm to optimize the wind tunnel for high-speed trains. Furthermore, we compare the advantages and disadvantages of different optimization schemes. Traditional optimization methods prove inefficient because of the system’s numerous variables and the presence of multiple peaks in the objective function. Inspired by the biogenetic breeding method, we introduce an optimization approach based on a specific gene mutation. This innovative method significantly reduces optimization time and improves efficiency by approximately 17%.

The Lunar Gravity Compensation Facility (LGCF) is a critical component in ground tests for a crewed lunar roving vehicle (CLRV). The track-following servo subsystem’s performance is of critical importance in the LGCF, as it needs to achieve high-precision tracking of the CLRV’s fast, wide range of motion in the horizontal direction. The subsystem must also operate within various constraints, including those related to speed, acceleration, and position. These requirements introduce new challenges to both the design and control of the subsystem. To tackle these challenges, this paper employs a Permanent-Magnet Synchronous Motor (PMSM) vector control method based on Space Vector Pulse Width Modulation (SVPWM) to achieve accurate speed tracking. Additionally, this paper presents an Explicit Model Predictive Control (EMPC) strategy for precise position servo control of the track-following system under multi-parameter constraints. The simulation model of the track-following servo subsystem is established based on the above methods. The simulation results demonstrate that the position tracking error of the gravity compensation system, constructed using the above method combined with EMPC control, is less than 0.2 m. The control performance of the EMPC is significantly better than those of the PI and LQI controllers. The influence of errors on the drawbar pull is within 12.5%, and its effect on the compensation force is negligible. These results provide theoretical support for the design of a track-following servo subsystem.

A new type dissimilar redundant actuation system (NT-DRAS), which is composed of an electro-hydrostatic actuator (EHA) and an electro-mechanical actuator (EMA), is applied in high value unmanned aerial vehicles such as the future near space vehicles to improve their reliability and performance index simultaneously. Further improvement in the flight safety is achieved with the fault-tolerant control (FTC) technique which deals with system faults. This paper proposes a novel convex optimization-based fault-tolerant control (CO-FTC) strategy for the NT-DRAS subject to gradual faults which are included in the state space representation of the system. A convex analysis-based treatment for system uncertainty caused by gradual faults is applied to determine the control gain matrix. The existence condition of the control gain matrix is optimized in the linear matrix inequality (LMI) form. Finally, the determined subsystems based on the novel technique is used to solve the modeled robust FTC problem. Case studies of NT-DRAS subject to different gradual faults have been accomplished to illustrate the FTC necessity for NT-DRAS. Furthermore, the effectiveness of the proposed CO-FTC strategy is validated by comparative analysis of the simulation results.

This paper deals with the modeling of the thermal load and the simulation of thermal dynamic characteristics for the hydraulic system of a large airliner in a full mission profile. Firstly, the formation mechanism of the thermal load in the hydraulic system is analyzed, and thermal dynamic modeling is conducted of the hydraulic components of an hydraulic system with an immersed heat exchanger employing the lumped parameter thermal node method and oil temperature and power loss of each key node within the hydraulic system within a full mission profile. Then, a thermal dynamic simulation model based on MATLAB/Simulink is established, and the temperatures at the nodes of different components and the absorptive capacity of the fuel heat sink in the thermal management module are calculated. The simulation results show that the thermal management scheme of the heat exchanger, located in the return oil pipeline of the hydraulic piston pump housing and immersed in the central fuel tank, can dissipate the thermal load of the system. This work is of important significance for temperature analysis and thermal load dissipation of the airliner hydraulic system.

As a critical system of onboard aircraft equipment, the environmental control system (ECS) has an essential impact on flight safety. The performance of the ECS is usually tested using the thermal test facility. The facility comprises temperature and pressure simulation units to simulate the engine bleed air. Currently, the ECS often fails due to the dynamic and rapid changes in the temperature and pressure of bleed air. To achieve the dynamic bleed air simulation, the most critical problem is to simulate the bleed air’s rapid heating and boost process during the actual engine working process. However, the temperature simulation unit has the characteristics of nonlinear and large inertia. Moreover, temperature and pressure control are strongly coupled. These characteristics usually lead to temperature and pressure dynamic control failure. This paper introduces a novel facility that adopted the hot and cold blending method to realize the rapid response of the temperature. Furthermore, it used a particular system structure to reduce pressure and temperature control coupling. In addition, it adopted the lookup-table-based PID (LPID) controller to acquire the rapid response and good steady-state performance of temperature and pressure control. Experimental control results are presented and discussed. The results showed that the facility could meet ECS’s dynamic and steady-state test requirements. The novel facility makes up for the insufficient dynamic test capacity of the previously developed ECS test facilities.